1. Field of the Invention
The present invention relates to the field of bipolar differential amplifiers.
2. Prior Art
Input offset voltage trimming, both at wafer sort and final test, has been used in various guises for decades.
It has long been known that the best noise and offset performance is obtained from an input stage comprised of a resistively loaded long tailed pair followed by subsequent gain stages. Such a configuration is shown in outline in FIG. 1. There are many ways to trim the input referred offset voltage but the preferred method is by modifying the current in R1 and R2. This can be accomplished, as shown, by changing the value of one of the load resistors, adding a compensating voltage or adding a compensating current. The correction circuitry needs to be implemented for both resistor loads as the error distribution is bipolar.